williams-et-al-1983-apple-ii-computer-graphics

CHAPTER 10-SHAPING UP 111Sections A and B contain the code to move up (00 ) fo r the first six bytes,arid section C contains the code to move left (11) for the fi rst five, whilethe sixth causes a move to the right. It may seem pretty silly to move to theleft in number 5 and then immediately right in number 6 instead of movingstraight up in both of them. Remember, however, that if number 5 wereonly to move up, it would be all zeros- 00 000 000-and would erroneouslysignal the end of the shape, so the small deception is necessary. Theremainder of the shape is digitized in the same manner as the saucer, soinstead of belaboring the point, just enter Monitor and type the shape tablegiven in Listing 1©-3.300 : 01 00 04 00 C4 C0 C0 C0308: C0 40 35 35 35 35 2B 4D310 : 09 89 3F 3F FF FF 3B FF318 : 2A 2D 2D 2D 2D 2D 2D 2D320 : lE 3F 3F 3F 3F 3F 3F 3F328: 17 2D 2D 2D 2D 2D 2D 2D330: 3E 3F 3F 3F 3F 3F 3F 37338 : 2D 2D 2D 2D 2D 2D 2D 15340 : 3F 3F 3F 3F 3F 3F 3F 3F348 : 2E 2D 2D 2D 2D 2D 2D 2D350 : 2D 15 3F 3F 3F 3F 3F 3F358 : 3F 3F 3F 0E 2D 2D 2D 2D360 : 2D 2D 2D 2D 3E 3F 3F 3F368 : 3F 3F 3F 3F 37 2D 2D 2D370 : 2D 2D 2D 2D 35 3F 3F 3F378 : 3F 3F 3F 3F 2E 2D 2D 2D380 : 2D 2D F5 3B 3F 3F 3F 4E388 : 2D 2D 05 00Listing 1 Cll-3. Apple shape table.The fi rst byte declares that there is one shape in the table, and thesecond byte is unused. The third and fourth bytes give you the offset forthe fi rst (and only) shape: 4 (remember lo-byte/hi-byte), and the fo llowingbyte is the beginning of the shape.Save the table (if you have a disk) by typingBSAVE APPLESHAPE,A$300,L$8CTo see what you have accomplished, typePOKE 232, 0 :POKE 233 ,3HGR:SCALE = l:ROT = 0DRAW 1 AT 100,100The first line tells the system where to find the table, the second is obvious,and the third draws the shape from that table on the Hi-Res screen. If youmanaged to get all of the numbers keyed in correctly, you will see a little